Hydraulic control system for refuse collection vehicle

ABSTRACT

A front loading refuse vehicle includes at least one positive displacement pump having an associated valve system in fluid communication with drive mechanism that operates a lifting arm, packer, a rear door of the vehicle, and a hoist for a refuse storage body. The valve system includes at least one closed-centered valve with a spool mechanism having a pressure compensator to maintain a constant flow rate of fluid through the valve regardless of differential in pressure across the valve for any given position of the spool mechanism. Two pumps with two separate hydraulic control systems are used with a side loading refuse vehicle. An electrical/electronic control system including a microprocessor operates the valve systems for each vehicle.

RELATED PATENT APPLICATION & INCORPORATION BY REFERENCE

This application is a divisional application of U.S. utility applicationSer. No. 10/850,052, filed May 20, 2004, now U.S. Pat. No. ______, whichclaims the benefit under 35 USC 119(e) of U.S. provisional patentapplication Ser. No. 60/471,944, entitled “Hydraulic Control System ForSide Loading Refuse Collection Vehicle,” filed May 20, 2003. Theserelated applications are incorporated herein by reference and made apart of this application. If any conflict arises between the disclosureof the invention in this divisional application and that in the relatedprovisional application, the disclosure in this divisional applicationshall govern. Moreover, the inventors incorporate herein by referenceany and all U.S. patents, U.S. patent applications, and other documentscited or referred to in this application or cited or referred to in theU.S. patents and U.S. patent applications incorporated herein byreference.

DEFINITIONS

The words “comprising,” “having,” “containing,” and “including,” andother forms thereof, are intended to be equivalent in meaning and beopen ended in that an item or items following any one of these words isnot meant to be an exhaustive listing of such item or items, or meant tobe limited to only the listed item or items.

BACKGROUND OF INVENTION

Refuse collection vehicles include front loading and side loadingvehicles for collecting refuse in containers placed on the side of astreet by home or business. Front loading refuse collection vehicles usea lifting arm mounted to move between a position above the cab of thevehicle and a position in front of the vehicle. The arm moves from theposition above the cab to the position in front of the vehicle, picks upa refuse container and lifts the container over the top of the cab,dumping the container's contents into the vehicle's refuse storage body.Side loading refuse collection vehicles use a lifting arm mounted on thevehicle's chassis or the refuse storage body. In side loading refusecollection vehicles, from a start position adjacent the side of thetruck refuse body, the arm is extended to reach a refuse container.

At the outer end of either the side-mounted or front-mounted lifting armis an apparatus that, upon actuation when positioned adjacent the refusecontainer, holds the container during lifting and dumping of thecontainer. A grabber mechanism is used with the side-mounted arm thatgrips the refuse container and a fork mechanism is used with thefront-mounted lifting arm that engages the refuse container. Both thegrabber and fork mechanisms typically require the holding apparatus tobe moved from a non-engagement position to an engagement position.

In both type of vehicles, the arm raises the container above the refusestorage body and tilts or inverts it to dump its contents into an openhopper in the top of the vehicle's refuse storage body. The lifting armwhile holding the empty refuse container is then moved downward to setthe container on the street. Finally, the arm is returned to its startposition. The refuse storage body includes a packer to compact therefuse inside the body and the body is mounted to be tilted by a hoistto allow collected refuse to be discharged through an open rear doorfrom the rear of the body. The rear door is closed while the packer isbeing operated and is opened to discharge the compacted refuse.

Different drive mechanisms have been used to operate the lifting arm,grabber mechanism, packer, the holding apparatus, and refuse storagebody, for example, hydraulic cylinders, hydraulic motors, andhydro-mechanical actuators. Most of the refuse vehicle manufacturingindustry uses gear pumps to operate these drive mechanisms. Such gearpumps are fixed displacement, low volumetric efficiency devices thatcannot vary the flow rate from the pump without changing speed (whichcannot be changed for control of output). These pumps supply the outputfluid to the open-centered directional hydraulic control valves thatsupply fluid to the desired functional cylinders, motors and/oractuators. As such these pumps are on-off systems where, if any functionis activated, all the fluid that is not used by the function is raisedto a relief pressure setting and spilled over a relief valve, convertingenergy into heat. At the same time the pump's enormous leakage (whichincreases as the pressure and/or temperature rises) generates more heatand less useful work. Even when no function is operated and the fluidjust flows through a valve, high flows cause large pressure drops thatresult in loss of energy into heat. To save energy at higher enginerevolutions, when the pump operation is not needed, devices such as “dryvalve” have been used to choke off the pump's inlet to stop the pumpfrom pumping fluid.

To increase the volumetric efficiency some manufacturers have used vanepumps. Vane pumps have a much higher volumetric efficiency and thusreduce the energy losses due to pump leakage. Nevertheless, all theother losses stay the same as in the gear pump. Another disadvantagethat vane pumps have is that unlike gear pumps, the flow from cannot becut off. The vane pump has to pump out fluid when it turns. To reducethe pressure drop that would take place when pumping all the fluidthrough a directional control valve, especially at higher engine/pumpspeeds, a by-pass valve is used that opens when a signal is supplied toit to connect the discharge of the pump to suction, thus looping thefluid. This lowers the losses comparative to pumping through the valve,but a considerable pressure drop across the bypass valve and line occursat higher speeds and results in major energy loss. To avoid raising allthe fluid to the relief valve pressure, some manufacturers have usedload sensing relief valves (unloading valves) to lower the reliefpressure to the functional requirement. However, this requires loadsensing directional control valves or other additional components. Inspite of all of these energy loss reduction efforts, the losses remainextremely high in these pump systems, resulting in very high operatingtemperatures (175-185° F.). This in turn results in even higher lossesdue to loss of viscosity, higher component wear, higher seal failures,and hydraulic fluid oxidation requiring fluid changes.

U.S. Pat. No. 6,312,209 discloses a front loading vehicle using avariable displacement piston pump supplying fluid to closed-centeredvalves to actuate drive mechanisms. Front loading refuse collectionvehicles are simple, slow moving systems that do not require thedynamics and controls necessary for side loading vehicles. This vehicleemploys directional control valves that cannot accurately and repeatablycontrol the speed of the lifting arm, since flow in these valves cannotbe precisely adjusted. The reason for this inaccuracy andnon-repeatability is pneumatic activation of the direction controlvalves: Besides the inaccurate and non-repeatable control achieved by acompressible pneumatic media, the system air pressure is not constantand results in different lifting arm speeds at the same control setting.

SUMMARY OF INVENTION

This invention provides a refuse collection vehicle having a controlsystem for achieving far superior results than obtained by pneumaticsystems commonly used by the refuse vehicle manufacturing industry. Thisinvention has one or more features as discussed subsequently herein.After reading the following section entitled “DETAILED DESCRIPTION OFSOME EMBODIMENTS OF THIS INVENTION,” one will understand how thefeatures of this invention provide its benefits. The benefits of thisinvention include, but are not limited to: (a) accurate and repeatablecontrol of valve operations and speed of movement of drive mechanisms,in particular the accurate control of the speed of the lifting arm in aside loading or front loading refuse vehicle, (b) improved energyefficiency, (c) reduced wear of drive mechanisms, and (d) extended lifeof the hydraulic fluid.

Without limiting the scope of this invention as expressed by the claimsthat follow, some, but not necessarily all, of its features are:

One, the refuse vehicle includes a lifting arm mounted to the vehiclethat moves between a lowered position and a raised position. This armmay be mounted on the side or front of the vehicle.

Two, a refuse storage body is mounted to move between a lowered positionand a raised position. It has a rear door that moves between a closedposition and an open position, and a packer in the refuse storage bodymoves between an extended and a retracted position.

Three, drive mechanisms connected to the lifting arm, refuse storagebody, rear door, and packer move the arm, body, rear door, and packerbetween their different positions.

Four, a hydraulic valve system operates the drive mechanisms. This valvesystem may include a plurality of valves having spool mechanismsmoveable to different positions in response to electronic actuationdevices to adjust the speed and direction of movement of the drivemechanisms.

Five, sensors detect the positions of the lifting arm, refuse storagebody, rear door, and packer, said sensors generating electrical signalscorresponding to said positions. At least one of the sensors maycontinuously monitor the position of the lifting arm and generate armposition signals.

Six, an electrical/electronic control system may include electronicactuation devices that, in response to the electrical signals, operatethe drive mechanisms. Also electrical/electronic control system mayinclude a microprocessor programmed to control the movement of the spoolmechanisms to adjust the speed and direction at which the drivemechanisms move. The microprocessor may include a program routineresponsive to position signals, with the program routine adjusting thespeed and direction of movement the drive mechanism for the arm. Theroutine may provide that the arm follow a predetermined motion profileso that the arm is accelerated and decelerated to minimize the cycletime. The routine may provide that the arm has a predetermined dwelltime for refuse to drop out of the refuse container when the arm is in adump position. A routine may be provided to timely and strategicallyplace decelerations of the arm to close a refuse container lid when thecontainer is returned to a start position. Another routine may providefor smooth starts and stops of the arm. Still another routine mayprovide for slowly and smoothly cushioning the stopping of the drivemechanisms at motion extremities of the drive mechanisms. Also, aprogram routine maybe provided for the drive mechanism for the packer tostop the packer smoothly and smoothly reverse the direction of movementof the packer. Another program routine may provide an interlockingsafety feature.

Seven, the microprocessor may include a program routine that provides aregenerative feature for at least one of the operational functions ofthe vehicle. The regenerative feature enables hydraulic fluid to berecycled between a cap side and a rod side of one of the valves. Thisone valve operates the drive mechanism for the lifting arm to controlthe down and out motion of the lifting arm. The regenerative featureenables a valve to operate the drive mechanism for the packer. Thisregenerative feature is enabled upon a predetermined pressure beingdetected by a pressure sensor monitoring pressure at an output end ofthis valve.

Eight, the electrical/electronic control system may include a pluralityof manually operated control devices mounted in a cab of the vehicle. Atleast some of the manually operated control devices are components of acontrol box in the cab, and at least some of the manually operatedcontrol devices include a plurality of warning lights, each light beingassociated with a different operational function of the vehicle.

Nine, the lifting arm may have a predetermined motion profile that is afunction of shaping of an electrical control signal. This motion profileis shaped so that the up/down motions of the lifting arm are acceleratedand decelerated to minimize the cycle time, allow time for refuse todrop out of the refuse container in a dump position, and provide timelyand strategically placed decelerations when the container is returned toground after dumping the refuse.

These features are not listed in any rank order nor is this listintended to be exhaustive.

DESCRIPTION OF DRAWING

Some embodiments of this invention, illustrating all its features, willnow be discussed in detail. These embodiments depict the novel andnon-obvious refuse vehicle of this invention as shown in theaccompanying drawing, which is for illustrative purposes only. Thisdrawing includes the following figures (Figs.), with like numeralsindicating like parts:

FIG. 1A is a side elevational view of a side loading refuse vehicle ofthis invention with the refuse storage body in a raised position.

FIG. 1B is a fragmentary top view of the side loading refuse vehicleshown in FIG. 1A with its lifting arm rotated 90 degrees.

FIG. 1C is a side elevational view of a side loading refuse vehicle ofthis invention showing the position of various sensors.

FIG. 2 is a perspective view of the lifting arm used in the side loadingrefuse vehicle shown in FIG. 1A.

FIG. 3 is a simplified schematic diagram of the hydraulic system for theside loading refuse vehicle shown in FIG. 1A.

FIG. 4 is a detailed schematic diagram of the hydraulic system for theside loading refuse vehicle shown in FIG. 1A.

FIG. 4A is an enlarged fragmentary view taken along line 4A of FIG. 4.

FIG. 5 is a perspective view of a valve system in fluid communicationwith a drive mechanism that operates the packer, rear door opener, andthe hoist for the refuse storage body of the side loading refuse vehicleshown in FIG. 1A.

FIG. 6 is an exploded view of the hydraulic system for the side loadingrefuse vehicle shown in FIG. 1A.

FIG. 6A is a parts list for the hydraulic circuit shown in FIG. 6.

FIG. 7 is an exploded view of the hydraulic system for the lifting armof the side loading refuse vehicle shown in FIG. 1A.

FIG. 7A is a parts list for the hydraulic circuit shown in FIG. 7.

FIG. 8 is an exploded view of the hydraulic system for the packer, therear door, and the hoist of the side loading refuse vehicle shown inFIG. 1A.

FIG. 8A is a parts list for the hydraulic circuit shown in FIG. 8.

FIG. 9 is a schematic diagram of the hydraulic systems for aconventional system I, a conventional system II, and the side loadinghydraulic circuit of this invention.

FIG. 10 is a table comparing the operational characteristics of thehydraulic circuits depicted in FIG. 9.

FIG. 10A is a schematic diagram of the electrical/electronic controlsystem used with the vehicle shown in FIGS. 1A and 1B.

FIG. 11A is a side elevational view of a front loading refuse vehicle ofthis invention.

FIG. 11B is a side elevational view of the front loading refuse vehicleshown in FIG. 11A with its refuse storage body raised and rear dooropen.

FIG. 12 is a simplified schematic diagram of the hydraulic system forthe front loading refuse vehicle shown in FIGS. 11A and 11B.

FIG. 13 is a detailed schematic diagram of the hydraulic system for thefront loading refuse vehicle shown in FIGS. 11A and 11B.

FIG. 14 is a schematic diagram of the electrical/electronic controlsystem used with the front loading refuse vehicle shown in FIGS. 11A and11B.

FIG. 15 is a perspective view of the control box used with the frontloading refuse vehicle shown in FIGS. 11A and 11B.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THIS INVENTION Side Loader

As illustrated in FIGS. 1A, 1B and 2, a side loading refuse vehicle 100of this invention includes a lifting arm 102 mounted on a side of thevehicle 100. The arm 102 has a grabber mechanism 104 (FIG. 2) thatincludes a pair of opposed grabber arms 106 that are moved towards andaway from each other to grip a refuse container (not shown) in aposition on the ground. The lifting arm 102 is moved from a startposition adjacent the side of the vehicle 100 to grip the refusecontainer, lift it over an open top of a refuse storage body 108,inverting the container to dump its contents through an open hopper 109into the refuse storage body 108, returning the container to itsposition on the ground, and finally back to its starting position. Therefuse storage body 108 includes a packer 110 (FIGS. 1B and 4) actuatedby a cylinder 15. The packer 110 includes a packer blade 110 a that,upon actuation of the packer, pushes refuse towards a rear door 112 tocompact the refuse. As shown in FIG. 1A, the compacted refuse isdischarged from the vehicle 100 upon opening of the rear door 112 andthe refuse storage body 108 being tilted by a hoist 108 a.

As best illustrated in FIG. 2, the lifting arm 102 includes a bracket104 a carrying a hydraulic cylinder 7 having its rod 7 a attached to aninverted V-shaped arm 7 b that is pivotably mounted at its proximal endto the bracket 104 a. The distal end of the inverted V-shaped arm 7 bhas a bracket 7 c carrying a hydraulic cylinder 9 that actuates thegrabber arms 106. A hydraulic cylinder 8 mounted at an inner end of thebracket 104 a has its rod connected to a slider member 7 d mounted tothe bracket 104 a to move in and out. The hydraulic cylinder 7 andV-shaped arm 7 b are carried by slider member 7 d and move in and outtherewith. A rotary position sensor RS1 continuously monitors theposition of the inverted V-shaped arm 7 b to detect the Up/Down positionof the lifting arm 104. A series of spaced apart bolt heads 7 e along aninner side of the slider member 7 d are used, along with a proximitysensor PS1, to monitor the In and Out positions of the lifting arm 104.

In accordance with this embodiment of the invention, two positivedisplacement pumps 2 and 3 mounted in front of the cab 124 (FIG. 1A) areemployed in the hydraulic circuit depicted in FIG. 3. The pump 3, withan associated first valve system including spool valves 12, 13, and 14,is in fluid communication with the hydraulic cylinders 15, 16, and 17that respectively operate the packer 110, the hoist 108 a, and the reardoor 112. The pump 2, with an associated second valve system includingspool valves 4, 5, and 6, is in fluid communication with hydrauliccylinders 7, 8, and 9 that operate the lifting arm 102. The spool valves4, 5, and 6 are mounted on the inner end of the bracket 104 a.

The spool valves 4, 5, 6, 12, 13, and 14 are each conventionalclosed-centered, pressure compensated valves. These spool valves 4, 5,6, 12, 13, and 14 each include a spool mechanism SM having a pressurecompensator PC to maintain a constant flow rate of fluid through thevalve regardless of differential in pressure across the valve for anygiven position of the spool mechanism. The highest load pressure amongstthe valves 4, 5, 6, and amongst the valves 12, 13, and 14 ishydraulically sensed automatically to adjust the pressure compensator PCto that pressure plus a predetermined additional amount of the operativepump 2 or 3, as the case may be. Additionally, the pressure compensatedflow through each closed-centered valve is maintained at a constant flowof hydraulic fluid (cylinder speed) regardless of pressures. The drivecylinder 15 for the packer 110 may also be controlled so that the packersmoothly stops and smoothly reverses direction through electronicshaping of a control signal in accordance with a program routine of amicroprocessor MP1 (FIG. 10A).

As illustrated in FIG. 10A, the speed and direction of movement of thespool mechanisms SM are controlled directly by an electrical/electroniccontrol system CS1. This electrical/electronic control system CS1, inaddition to the programmable microprocessor MP1, includes solenoidsSOL1, SOL2, SOL3, SOL4, SOL5, SOL6, SOL7, SOL8, SOL9, SOL10, SOL11, andSOL12. These solenoids SOL1, SOL2, SOL3, SOL4, SOL5, SOL6, SOL7, SOL8,SOL9, SOL10, SOL11, and SOL12, upon being energized, move a selectedspool mechanisms SM without the use of an external drive media such aspressurized air. The electrical/electronic control system CS1 controlsthe speed and direction of movement of a selected valve spool mechanismSM in response to the vehicle's operator actuating a manually operatedcontrol device (switches, joystick, etc.). The programmablemicroprocessor MP1 is programmed in accordance with conventionalprogramming procedures.

The lifting arm 102 may have an automatic mode of operation and a manualmode of operation that allows the vehicle's operator to manually controlthe speed and direction of movement of the arm. In the automatic mode,the lifting arm 102 has a predetermined motion profile that is afunction of shaping an electrical control signal by a routine of themicroprocessor's program. In an automatic mode, the Up/Down and In/Outmotions of the lifting arm 102 follow the predetermined motion profile.In a manual mode, the position of a joystick 10 (FIG. 10A) in thevehicle cab 124 determines the speed and direction of the arm movement.The microprocessor MP1 may have a program routine that provides asmooth, electro-hydraulically ramping up and stopping of the arm's drivecylinders 7, 8 and 9 to cushion starts and stops whether in theautomatic or manual mode.

Referring to FIGS. 3 and 4, the pump 2, a variable displacement,pressure compensated, load-sensing piston pump, draws fluid from areservoir 1 through a suction strainer (not shown) and an isolationvalve (not shown) and pumps it to the second valve system comprising thethree closed-centered, pressure compensated load-sensing valves 4, 5,and 6. The valve 4 supplies the fluid to Up/Down hydraulic cylinder 7when energized upon receiving a control signal generated using atwo-axis joystick 10 (or a proportional switch or similar manuallyoperable control member) in the cab 124 of the vehicle 100. As discussedin greater detail subsequently, a control box CB1 in the cab 124 and thejoystick 10 allows a vehicle operator to control the position of thelifting arm 104, grabber mechanism 104, refuse storage body 108, reardoor 112, and packer 110. The speed and direction of movement of thecylinder 7 is controlled by the hydraulic flow supplied to it, which inturn is controlled by the movement of the spool mechanism SP in itscontrol valve as regulated by the operation of the joystick 10. Thisspeed and direction of movement is only governed by the hydraulic flowand is not affected by the pressure differential between the fluidsupplied by the pump 2 and the pressure required by the load.

The valve 5 operates the cylinder 8 that moves the lifting arm 102 Inand Out using similar control as the valve 4 using a separate or the2^(nd) axis of the same joystick 10, yielding complete and precisecontrol of the In and Out movement of the arm. Conditioning the suppliedsignal to the valves to control movement provides the ability toaccelerate/decelerate and stop the arm smoothly and provide the motioncontrol needed to incorporate motions that would close the lids when theempty refuse container is rapidly brought down from the dump position inthe automatic mode. It also allows the use of a microprocessor MP1 (FIG.10A) to program in automatic functions, interlocks, and safeties notpossible with any other system without the use of extraneous devices.These extraneous devices increase system complexity and cost and reducereliability and availability of the system. The valve 6 operates theOpen/Close function of the arms 106 that grab the refuse container bysupplying fluid to the cylinder 9 via the valve 6 with its pressurecompensator PC adjusted to set the pressure of the grabber arms 106 toachieve a grabbing pressure that does not damage the container. The arm102 then lifts the container to dump its contents into the refusestorage body 108.

The fluid supplied by the pumps 2 and 3 is totally controlled by whatthe system requires at that time. When none of the functions areoperated, no flow is produced by the pumps 2 or 3 (the pump going toalmost zero displacement). When a function is energized, the flowproduced by the pump 2 or 3 would be what would be required as set byits associated valve. The pump 2 and 3 are equipped with dual pressurecompensators 2 a and 2 b and 3 a and 3 b, respectively, for setting apredetermined maximum pressure for the valve system to which they arerespectively connected, The compensators 2 a and 2 b ensure that thehydraulic system including the valves 4-6 never exceeds, for example,200-300 psi (a standby pressure above what the system requires), sensingpressure in a load-sensing hydraulic line 2 c. The compensators 3 a and3 b ensure that the hydraulic system including the valves 12-14 neverexceeds, for example, 3000 psi, sensing pressure in a load-sensinghydraulic line 3 c. This virtually eliminates or dramatically reduces,the losses encountered in the other hydraulic systems. In addition, thevery high volumetric efficiency (in the mid-nineties) reduces losses dueto leakage. Both of these result in the system running very cool,approximately 40 degrees F. cooler than the conventional systems.

To operate the refuse storage body functions (the packer 110 operation,the hoist 108 a to lower and raise the refuse storage body 108, and therear door 112), the pump 3 is used to supply the on-demand fluid. Thepump 3 is also a variable displacement, pressure compensated, loadsensing piston pump that supplies the fluid to a closed-centered,pressure-compensated, bank of directional control valves 12, 13, and 14.The pump 3 may be mounted in tandem with pump 2 as shown in FIG. 3, orseparately. The valve 12 operates the packer cylinders 15, the valve 13operates the hoist cylinders 16, and the valve 14 operates the rear doorcylinders 17. These pressure compensated valves 12-14 allow a presetmaximum speed of each drive cylinder.

As shown in FIG. 10A, the electrical/electronic control system CS1includes the programmable microprocessor MP1, control box CB1, rotaryposition sensor RS1, joystick 10, and solenoids SOL1, SOL2, SOL3, SOL4,SOL5, SOL6, SOL7, SOL8, SOL9, SOL10, SOL11, and SOL12. In addition, theelectrical/electronic control system CS1 includes proximity sensors PS1,PS2, PS3, PS4, PS5, and PS6 for detecting the movement of the liftingarm 104, grabber mechanism 104, refuse storage body 108, rear door 112,and packer 110. The proximity sensor PS1 is located adjacent on thebracket 104 a as shown in FIG. 2. The proximity sensor PS2 is located onthe bracket 104 a inward of the sensor PS1 as shown in FIG. 2. Theproximity sensor PS3 is located inside the refuse storage body 108 nearthe cab 124. The proximity sensor PS4 is located nearby sensor PS3 asshown in FIG. 1C. The proximity sensor PS5 is near a hinge for the reardoor 112. The proximity sensor PS6 is located beneath the refuse storagebody 108 along a refuse storage body support structure 108 b as shown inFIG. 1A.

The proximity sensors PS1, PS2, PS3, PS4, PS5, and PS6 generate signalsthat are processed by the microprocessor MP1 in accordance with itsprogram to energize the solenoids SOL1, SOL2, SOL3, SOL4, SOL5, SOL6,SOL7, SOL8, SOL9, SOL10, SOL11, and SOL12. When energized the solenoidSOL1, by moving the spool mechanism SM of the associated valve 12 thatcontrols the operation of the packer hydraulic cylinder 15, extends thepacker blade 110 a. When energized the solenoid SOL2, by moving thespool mechanism SM of the valve 12 in the opposite direction, retractsthe packer blade 110 a. When energized the solenoid SOL3, by moving thespool mechanism SM of the associated valve 14 that controls theoperation of the rear door hydraulic cylinder 17, closes the rear door112. When energized the solenoid SOL4, by moving the spool mechanism SMof the valve 14 in the opposite direction, closes the rear door 112.When energized the solenoid SOL5, by moving the spool mechanism SM ofthe associated valve 13 that controls the operation of the refusestorage body hoist hydraulic cylinder 16, lowers the refuse storage body108. When energized the solenoid SOL6, by moving the spool mechanism SMof the valve 13 in the opposite direction, raises the refuse storagebody 108.

When energized the solenoid SOL7, by moving the spool mechanism SM ofthe associated valve 4 that controls the operation of the lifting armup/down hydraulic cylinder 7, raises the lifting arm 104. When energizedthe solenoid SOL8, by moving the spool mechanism SM of the valve 4 inthe opposite direction, lowers the lifting arm 104. When energized thesolenoid SOL9, by moving the spool mechanism SM of the associated valve5 that controls the in/out operation of the lifting arm hydrauliccylinder 8, retracts the lifting arm 104. When energized the solenoidSOL10, by moving the spool mechanism SM of the valve 5 in the oppositedirection, extends the lifting arm 104. When energized the solenoidSOL11, by moving the spool mechanism SM of the associated valve 6 thatcontrols the operation of the grabber arms hydraulic cylinder 9, opensthe grabber arms 106. When energized, the solenoid SOL12 by moving thespool mechanism SM of the associated valve 6 in the opposite direction,closes the grabber arms 106.

The control box CB1 has a toggle switch TS1 for activating the up anddown position of the refuse storage body 108, a toggle switch TS2 foractivating the open and closed position of the rear door 112, a toggleswitch TS3 for enabling the control box CB1, and a toggle switch TS4 forenabling the joystick 10. This control box CB1 has a push button 150that the vehicle operator presses to activate an automatic operationalmode for the packer 110, which may have one or more cycles. A rockerswitch 152 on the control box CB1 allows the vehicle operator tomanually control the operation of the packer 110. An emergency stopbutton 154 is also provided. Conventional electrical connectors CONconnect together the electrical lead lines and components of theelectrical/electronic control system CS1.

To reduce flow requirements and reduce cycle times, another programroutine may provide a regenerative feature for the Extend motion of thepacker 110 during compacting refuse and a regenerative feature for theDown and Out motions of the lifting arm 102. The regenerative featuresimply means that the hydraulic system is enabled to recycle hydraulicfluid between a cap side and a rod side of one of pistons (not shown),for example, the valve 12 in FIG. 4A.

For the packer regenerative feature, the spool mechanism SP1 of valve 12has a plurality of position, pos. 1, pos. 2, pos. 3, and pos. 4.Initially, the spool mechanism SP1 is in a position where the packerdrive cylinders 15 generate a relative low pressure. A pressure sensor18 (FIG. 4) detects a predetermined elevated pressure as the packer 110gradually increases its pressure as the refuse collects in the refusestorage body 108. The pressure sensor 18 provides an electronic signalfor fluid to be recycled. In pos. 1 the spool mechanism SP1 blocks allthe valve's ports. Pos. 2 is the retract position where fluid issupplied to the rod side of the packer cylinders 15 to retract thepacker 110. Pos. 3 is a regenerative configuration of the spoolmechanism SP1 in that the pump pressure is connected to both the rod andthe cap side of the cylinder to extend the cylinder.

This regenerative feature reduces the flow requirement from the pump 3,dramatically reducing the cycle time and saving energy. Since theinitial travel of the blade 110 a of the packer 110, and until therefuse storage body has been packed with refuse, does not require thehigh compaction forces, this feature saves considerable energy andreduces pump size requirements. In one embodiment of this invention, thepressure sensor 18 is set at 2800 psi, and closes when the pressure inthe cap side reaches this pressure. The sensor then supplies a signaland the program routine lowers the voltage to the solenoid SOL1 thatcontrol the operation of the packer in its extended position, moving thedirectional control spool mechanism SP1 of the valve 12 to the positionpos. 4. This allows the full force of the cylinders 15 to come into playto compact the refuse in the refuse storage body 108 for higherpayloads.

In a similar manner the lifting arm 102 may uses a regenerative feature.No sensor is required, however. The regenerative feature for the liftingarm 102 is operative only when the arm moves down and out when lowerpressures are needed. Both the down direction of the Up/Down cylinder 7and out of the In/Out cylinder 8 use “regenerative” directional controlspool mechanisms of these valves. This regenerative feature reduces thedemand on pump fluid supply dramatically reducing it to the rod volumeonly rather than the high fluid volume required to supply the cap sideof the cylinder. The resulting loss of force in both cases has no effecton performance since very little force is required in this mode of thecylinder movement. The use of the regenerative feature increases the armspeed and dramatically reduces pump flow requirement and thus the pumpsize.

The microprocessor MP1 may be programmed to include at least one routinethat provides an interlocking safety feature to thereby avoid the use ofexternal pneumatic mechanisms and valves. For example, a sensorPS—detects when the refuse storage body 108 has been titled upward. Theprogram routine in this case would, in response to the sensorPS—detecting this condition, prevent the packer 110 from operating.

Another program routine provides for the drive cylinders 15 for thepacker 110 to stop smoothly and smoothly reverse direction of movement.

Another program routine provides for direct control of a valve to allowmanual control for motion modification where required, such as in thepacker 110 where the packer is decelerated to a stop and reversed indirection without the use of external “Deceleration Valves” used by someprior art vehicles to avoid hard stops.

FIGS. 9 and 10 compares two conventional systems (conventional gear pumpsystem I and conventional vane pump system II) with the hydrauliccontrol system of the present invention discussed above. Referring toFIG. 9, the first column A shows a conventional gear pump with a dryvalve. The center column B shows a vane pump with load-sensing control,and the third column C shows high pressure, pressure-compensated, loadsensing piston pump system with pressure compensated flow controldirectional valves of the present invention. Since the normal vane pumpsystems are not load-sensing, only the right column of the vane pumpapplies. This also means that the fuel losses of this system will beconsiderably higher than shown on the chart. Please note the comparativelosses and fuel saving with our system compared to the gear and the vanepump systems. The very fact that to-date, even in 110° F. ambienttemperatures, the system temperature of this invention, with a 45 gallonreservoir, has never exceeded 142° F., is a testimony to the efficiencyof this invention and longevity of the hydraulic components it produces.In addition to all that, the very complex and expensive hydraulicplumbing that the vane pump system requires, in addition to moreexpensive Viton seals, is a lot more than the difference in price of thetwo pumps, and replacing the vane pump requires considerable amount ofmore labor than the piston pump with its one suction, one supply and onesmall load-sense line and no electrical connections.

The operating figures have repeatedly indicated that both theconventional systems I and II operate at temperatures of 180 to 185degrees Fahrenheit. This is the temperature at which the lubricity andviscosity go down dramatically, increasing system leakage (whichtranslates into lower volumetric efficiencies and higher heatgeneration). Couple to that fact is the cost of hydraulic fluidreplacement, higher failure rate of other components, such as valves andcylinders due to excessive temperatures, not to speak of its higher fuelconsumption. Compared to that the lower prices of the gear or vane pumpsbecome inconsequential.

Whereas the vane pump offers a higher volumetric efficiency than gearpump, it suffers from the problem of not being able to stop the flowthrough the pump that is directly proportional to the engine speed. Allthe flow has to go through the valves creating a very high pressuredrop, which is synonymous with power loss and heat generation, until thepump is cut out at higher speeds by an Oasis card. At highway speeds at2200 rpm, the arm pump and the packer pump produce very high flows thattry to loop around from the discharge sides to the suction side of thepump creating not only a high pressure drops but also the turbulencethat entrains air and causes cavitation in the pump, causing pump portplate erosion and pump failure. Additionally with a 60-gallon hydraulicreservoir, even at system operational speeds with a flow ofapproximately 80 gpm, the residence time of the fluid in the hydraulictank is only 45 seconds, whereas hydraulic systems require approximately2 minutes of residence time to purge the entrained air from thehydraulic fluid. This air in the system not only causes noise, it alsoshortens the pump and all hydraulic components life. Additionally, dueto these inefficiencies, this system runs at 180 degree Fahrenheit. Atthis temperature the hydraulic fluid begins to oxidize and deplete theanti-wear zinc additives thus requiring frequent fluid changes if thesystem life is to be maintained. Secondly, at this temperature thenormally 10 W hydraulic fluid has a viscosity of less than kerosenereducing the volumetric efficiency dramatically. Since a Denison vanepumps do not have pressure-balanced port plates the gap between thesides and the vane blades increases causing even higher leakage.

The gear pumps fare far worse where the volumetric efficiencies are verylow to start with and worsen rapidly to yield higher efficiency lossesthan the vane pump. Whereas a dry valve can be used to stop the highflow at higher speeds, the high leakage at relief pressures, allpressure dumping over the relief valve, and the rapidly declining pumpefficiencies, make that the worst choice in terms of power consumption.It wastes a lot of fuel as can be seen from the attached comparisonchart.

The pump efficiencies are factual efficiencies obtained at thesetemperatures. The gear pump volumetric efficiencies decline very rapidlywithin a few months of operation. The losses shown in bold fonts at thebottom of the chart are averaged for operation at the two pressures and750 and 1200 rpm operation. The obtained value is again averaged with a50% duty cycle where the collection operation is only 50% of the timewith the rest driving. Actual figures are lot higher for collectionoperation. Also the thermal efficiency in translating the energy loss tohorsepower assume a 42% thermal efficiency of diesel engines, a figurenot achieved by domestic diesel engines, which run around 36-38%. Assuch, these savings are considerably understated.

Front Loader

As shown in FIGS. 11A and 11B, the front loading refuse vehicle 200 ofthis invention includes a pair lifting arms 202 (only one shown), eachmounted on one side of the vehicle, to move between a raised positionshown in solid lines in FIG. 11A and a lowered position in front of thecab 201 a shown in dotted lines in FIG. 11A. Pins 202 c (only one shown)attached the arms 202 to the refuse storage body 108 to rotate betweenthe raised and lowered positions. A pair of forks 202 a is pivotablyconnected to the arms 202, so that with the arms lowered, and the forksrepositioned, these forks may be pushed into a pair channels in a bintype container (not shown) aligned with the forks. This embodiment ofthe invention only employs a single positive displacement pump 204 (FIG.12) mounted in the cab 201 a(FIG. 11A). Also the refuse storage body 108has a front door 203 that provides access to the inside of the refusestorage body.

As depicted in FIGS. 11B and 12, the pump 204 has an associated valvesystem 206 mounted on the refuse storage body 108. The valve system 206includes six spool valves a through f in fluid communication with thehydraulic cylinders 208, 210, 212, 214, 216, and 218. The cylinders 208are actuated to extend and retract the forks 202 a, the cylinders 210are actuated to raise and lower the arms 202, the cylinders 212 areactuated to operate the hoist 108 a to raise and lower the refusestorage body 108 (the same in both vehicles), the cylinders 214 areactuated to open and close the rear door 112 (same in both vehicles),the cylinder 216 is actuated to open and close a top door 201 on the topof the refuse storage body 108, and the cylinders 218 (FIG. 12) isactuated to operate the packer 110 and its blade 110 a (same in bothvehicles).

As illustrated in FIG. 12, the spool valves a through f are in fluidcommunication with these hydraulic cylinders 208, 210, 212, 214, 216,and 218 and each cylinder is a conventional closed-centered, pressurecompensated valve like those discussed above in connection with the sideloading vehicle 100. These spool valves a through f each include a spoolmechanism SM having a pressure compensator PC to maintain a constantflow rate of fluid through the valve regardless of differential inpressure across the valve for any given position of the spool mechanism.The highest load pressure amongst the valves a through f is sensedhydraulically to adjust the pressure compensator to that pressure plus apredetermined additional amount of standby pressure. As with the sideloader, the pressure compensated flow through each closed-centered valveis maintained at a constant flow of hydraulic fluid (cylinder speed)regardless of pressures.

The position of the spool mechanism SM may be controlled directly by anelectrical/electronic control system CS2 that moves the spool mechanismwithout the use of an external pneumatic drive media such as pressurizedair. The electrical/electronic control system CS2 controls the positionof the valve spool mechanism SM to vary the speed and govern thedirection of movement of hydraulic cylinder to which a valve is incommunication. The electrical/electronic control system CS2 may includea programmable microprocessor MP2 (FIG. 14) having program routines forcontrolling the different functions.

In accordance with this embodiment of the invention, the pump 204 is avariable displacement, pressure-compensated, load-sensing, piston pumpcapable of producing 5,000 psi but running at 3000 psi to power thefront loading functions. The pump 204 produces only the flow required toperform the function called for by the valve system 206. The pump 204 ismounted in front of the engine between the radiator and the front bumperand driven by a propeller shaft mounted on the front engine crankshaftdamper. The pump 204 sucks hydraulic fluid from the hydraulic fluidreservoir 222 through a 100-micron suction filter 226 and an isolationvalve 215. The high-pressure discharge flow from the pump 204 passesthrough a 10 micron high pressure filter 217 and supplies the flow tothe pressure-compensated, load-sensing, electro-hydraulic,close-centered valve system 206.

As depicted in FIG. 14, the valve system 206 receives electronic controlsignals through the programmable microprocessor MP2 of theelectrical/electronic control system CS2 to energize each function asrequired. The microprocessor MP2 is mounted inside a control box 254(FIG. 15) in the vehicle operator's cab 201 a. Solenoids SOL14 throughSOL19 are On/Off solenoids used to control the operation of the top-door201, rear door 112, and the hoist 108 a for the refuse storage body 108.The solenoids SOL20 through SOL25 are Pulse Width Modulation (PWM)solenoids that position a valve to set the flow therefrom according tothe position of its spool. The solenoids SOL20 through SOL25 inconjunction with other components of the electrical/electronic controlsystem CS2 control the operation of the arms 202, forks 202 a, andpacker 110. Proximity sensors PS8, PS9, PS10, PS11, PS12 and a rotaryposition sensor RS2 are used in a similar fashion to the comparablesensors used in connection with the vehicle 100. A series of warninglights L1 through L6 are on the control box 254. Components of theelectrical/electronic control system CS2 also include a packermanual/automatic switch SW2, a packer extend/retract switch SW3,auxiliary switch SW4, a top door switch SW5, a rear door switch SW6, amulti-pack select switch SW7, a refuse storage body switch SW8, anautomatic start packer push button PB1, a rear door safety button PB2, arefuse storage body safety button PB3, and an automatic stop/reversepacker push button PB4. The push button PB4, which is red in color andmushroom shaped, is an emergency stop control. Conventional electricalconnectors CON connect together the electrical lead lines and componentsof the electrical/electronic control system CS2.

FIG. 11A shows the location of the sensors PS8, PS9, PS10, PS11, PS12and RS2. The sensor PS8 that detects the position of the front door 203is located adjacent this door. The sensor PS9 that detects the positionof the packer blade 110 a is located inside the refuse storage body 108to one side. The sensor PS10 that detects the position of the top door201 is located near an end of the top door 201. The sensor PS11 thatdetects the position of the rear door is located next to a hinge 113that attaches the rear door 112 to the refuse storage body 108. Thesensor PS12 that detects the position of the refuse storage body 108 islocated along the refuse storage body support structure 108 b. Therotary position sensor RS1 continuously monitors the position of thearms 202 as they rotate to detect the arms' up/down position.

The pressure compensation feature of the valves a through f keeps theflow, and hence speed, constant regardless of the pressure variation forthat function for any position of an input device such as, for example,the joysticks 250 and 252 (FIG. 14) in the cab 201 a. The joystick 250is a Hall effect single-axis joystick and the joystick 252 is asingle-axis joystick. The load-sensing part of a valve senses thefunction pressure requirements and supplies a pressure signal to itsload-sensing pressure compensator PC to limit the pump pressure to thatvalue. In effect, this invention only produces the flow required and atthe pressure required. Also, no flow goes through a valve to the returnlines unless the return flow is generated by the energized function.Thus, no energy is wasted and no relief valves are used. (All valves athrough f are each equipped with a manual over-ride to activate thefunction in case the electrical/electronic control system CS2 sustainsdamage or fails. The over-ride can be activated with a small screwdriver by pushing into a slot in a solenoid-mounted male half of anelectrical connector CON, after un-plugging the female half of thisconnector CON.)

As depicted in FIG. 12, the return flow from the valve system 206discharges into a hydraulic reservoir 222 through a 10-micron returnfilter 219. The 45 gallon hydraulic reservoir 222 includes a suctionstrainer 226, a 10 micron breather cap 221, a drain plug 227, anisolation ball-valve 215, an electrically operated “Dyna Jack” 223, anda hydraulic fluid level sight gage-thermometer combination thatindicates fluid level and temperature (not shown). The “Dyna Jack” 223is a back-up device that is electrically powered to raise the refusestorage body 108 if the engine or the hydraulic system becomesin-operable, thus allowing access to the control valves and the chassismounted hydraulics or chassis components. The valve d that raises orlowers the rear door 112, raises this door through two cylinder-mountedcounter-balance valves 214 a and 214 b (FIG. 12). This ensure that evenif the hydraulic line to either or both cylinders 214 gets removed, cut,or disconnected, the rear door 112 would stay in its position and wouldnot drop. Similarly, an externally mounted single counter-balance valve259 would not allow the door 112 to move up or open unless the controlvalve d commands it to do so.

The command and control functions are provided by the microprocessor MP2in conjunction with the selective actuation of the switches SW1 throughSW1 and the push buttons PB1 through PB4 and the joysticks 250 and 252.The joysticks 250 and 252 enable the vehicle's operator to control themovement and speed of the arms 202 and the forks 202 a. By manipulatingthe position of the joysticks 250 and 252, the operator controls thespeed of movement. The farther a joystick is pushed, the faster themovement of the arms 202 and the forks 202 a. The lights L1 through L6work only when the power to the control box is turned on by pushing a‘Power’ rocker switch SW1 On when the ignition switch of the vehicle 200is also On to indicate that the power is available at the control box254. The push button PB4 would also light up to indicate that the powerto the control system CS2 has been turned ON.

The microprocessor MP2 may be programmed to include a routine providingat least one interlocking safety feature to avoid the use of externalsafety device. For example, the interlocking safety feature may bepreventing tilting of the refuse storage body 108 if the front door 203is open or preventing the operation of the lifting arms 202 if the topdoor 201 is open.

Operation

The systems of the vehicle 200 are designed to operate all controlfunctions at engine low idle (750-800 rpm). The fluid flow required byeach function is controlled by the valve system 206 and the electroniccontrol system CS2. Load or the engine speed does NOT change the speedof any function. Therefore, raising engine speed does not increaseoperational speed and only wastes fuel. The operation of this embodimentof the invention is as follows:

To Start

Start the vehicle's engine and turn On the power to the control systemCS2 by turning on the Power rocker Switch SW1 (FIG. 15). Check toconfirm that the rear door 112 is closed (Rear Door light L6 is Off).Check to confirm that the refuse storage body 108 is down (the Bodylight L4 is Off). Check to confirm that the top door 201 is fully open(the Top door light L5 is On). The arms 202 would not function unlessthe top door 201 is fully open. Confirm that the front access door 203is fully closed and the sensor light L5 is ON.

After starting and warming up the hydraulic system, check the highpressure filter condition light L1 on the control box 254. If the lightL1 is on, that means that a high pressure filter 300 (FIG. 13) isplugged and has gone into the “By-Pass” mode. Do not operate thehydraulic system for more than an hour under this condition and replacethe high pressure filter 300 as soon as possible. Check the condition ofthe return line filter 219 of the reservoir 222. This filter 219 may beequipped with a gage, 25 psi of differential pressure across the filterelement opens a by-pass valve and the fluid starts going around thefilter element, i.e. unfiltered fluid starts to go through the filter.If the filter 219 is equipped with a “Pop-Up” sight gage, a popped upindicator represents the same plugged filter condition. An electricindicator that will turn on a light on the control box 254 is alsoavailable as an optional feature. Operation with either of the filtersin the by-pass mode should be avoided.

Loading Arms

The front loading arms 202 are operated by the joystick 252. Moving thejoystick 252 towards the operator's body (as marked on a label “Up”)will raise the arms 202, and pushing it away from the operator's bodywill lower the arms 202. Two modes of operation are provided for themovement of these arms 202. On the control box 254 the rocker switch SW2shows “Automatic” and “Manual” positions. Only the “Automatic” positionof the switch SW2 puts both the arms 202 and the packer 110 in automaticoperation, whereas “Manual” position would put both the arms and thepacker in “Manual” operation mode. In the “Manual” position, the controlof the arms 202 is only designed for shop use. The automatic arm speedcontrol function does not work in this “Manual” position. In the“Automatic” mode, the arms 202 automatically slow down to a smooth stopat the “Up” position and at the preset “Down” position.

A preset “Down” position is set through an arm calibration procedureonly by the shop personnel. The “Down” position is set to allow stabbingthe forks 202 a into the channels of a lowest bin type container.Between the “Up” and “Down” position extremes, the vehicle operator hascomplete control of the speed of the arms 202. The farther the joystick252 is moved, the faster would the arms travel. Because the valve system206 is pressure compensated, the position of the arms 202 would thuscontrol the speed of arms regardless of the load on the arm or theengine speed. At near the end of the “Down” and “Up” positions theprogram of the microprocessor MP2 takes control to slowdown smoothly thearms 202 to a stop.

To safeguard against banging the arms 202 into a rubber cushion arm stop112 a (FIG. 11A) on the “Up” positions, and against the end of thecylinder 210 in the “Down” position, an automatic safety stop program isa routine that is built into the microprocessor MP2. In accordance withthis invention, an automatically “cushion” limits arm movement byslowing down the arms 202 to a smooth stop without banging the rubbercushion arm stop 112 a or the cylinder 210. The vehicle operator canease off on the joystick 252 to stop higher than the preset “Down”position to pick or release a container that is higher than the “Down”position. The operator would need to exercise control to make sure thatthe containers are not banged into the ground. If the arms 202 arerequired to go below the set “Down” position, depressing button PB4 willallow the arms to go lower slowly. To move up, the joystick 252, whichis operational at all time, is used.

Fork Control

The operation of the forks 202 a is a single function controlled by thejoystick 250. The vehicle operator by manipulation of the joystick 250controls the “Up” and “Down” movement of the forks 202 a. As with thecontrol of the arms 202, pushing the joystick 250 away from theoperator's body lowers the forks 202 a. Pushing the joystick 250 towardsthe operator's body raises the forks 202 a. Like the arms 202, the forkcontrol function is also proportional. The farther the joystick 250 ismoved, the faster the forks 202 a move. Again, each joystick positioncorresponds to a certain fork speed that would not change regardless ofthe load or the engine speed. Caution should be exercised to make surethat the forks 202 a are in the fully “UP” position before moving thevehicle 200 to avoid ramming the forks into elevated structures in thearm “Up” position, or running the forks into people or objects in frontof the vehicle in the arm “Down” or in front of the cab position.

Packer Control

When the “Automatic/Manual” rocker switch SW2 is in the “Manual” mode,the packer 110 can be moved inward by depressing the spring-centeredrocker switch SW3 marked “Packer” at the Extend end, or outward bypressing the rocker switch SW3 at the Retract end. Releasing the switchSW3 would stop the packer 110 at the position the packer 110 is at whenthe switch SW3 is released. In the “Automatic” Mode, the packer cyclemay be initiated by pressing the button PB1. Once this button PB1 isdepressed, the packer 110 goes through a complete automatic cycle ofextending and retracting before coming to rest in the retracted positionunless the button PB4 is pressed to stop at an intermediate position.The automatic cycle of extending and retracting the packer 110 is inaccordance with a routine provided by the program of the microprocessorMP2. In the “Automatic” mode, two packer cycle operations may beavailable using the rocker switch SW7. Depressing the switch SW7 to aposition marked “1” makes the packer 110 go through One Cycleautomatically once the “Start” button PB1 is pressed. Position “2”cycles the packer 110 twice before it parks itself in the retractedposition in accordance with another routine provided by the program ofthe microprocessor MP2. The “packer” light L3 comes on as soon as acommand to operate the packer 110 is given in either the “Manual” or the“Automatic” modes.

Rear Door Control

The rear door 112 is operated by actuation of the rocker switch SW6.However, to prevent inadvertent or accidental opening of the door 112,the rocker switch SW6 operation would NOT open or close the door. Therocker switch SW6 is only enabled by depressing and holding down thebutton PB2. In other words, first depress and hold the button PB2 beforedepressing the switch SW6 to Open or Close the rear door 112.

Top Door Control

The switch SW5 is the control for the top door 201. This switch SW5 isspring centered in a neutral position. Depressing the open side of thisswitch SW5 opens the top door 201 and depressing the closed side closesthe top door. The arms control function of the program of themicroprocessor MP2 does not allow the arms 202 to move upward if the topdoor 201 is not fully open.

Refuse Storage Body Hoist Control

The refuse storage body hoist control is also protected by the programof the microprocessor MP2 against inadvertent operation to safeguardagainst rollover of the vehicle 200. b. The switch SW8 controls theoperation of the refuse body hoist 108 a. This spring neutral rockerswitch SW8 can be depressed in either a “Body Up” or “Body Down”position to operate the hoist 108 a c. The control function would not beenabled unless the button PB3 is depressed and held down.

Optional Arm Control

An optional feature may be a routine in the program of themicroprocessor that eliminate control of the attitude of the arms 202and forks 202 a by the vehicle operator. With such a routine, thevehicle operator only has to stab the forks 202 a into the container,depress a button (not shown) on the joystick 252 and yank and hold thisjoystick. The forks 202 a automatically adjust to maintain containerattitude according to the arm position to ensure that the container doesnot hit the cab or its canopy. The arms 202 would lift the container tothe refuse storage body, dump the load, and return the containerstopping at the height automatically where the button on the joystickwas pressed to start the automation.

General

The electrical/electronic control systems of both vehicles 100 and 200provide direct control of the spool mechanisms SM of the valves throughthe use of “Pulse-Width Modulation (PWM)” or analog voltage or currentmodification. This not only brings about precise control that is notavailable through a compressible pneumatic media such as air (that movesthe spool mechanisms of the valves in the conventional systems), it alsois unlike such pneumatic systems where a noticeable time lag is present.Thus, this invention makes the control of each control function precise,predictable, and repeatable in addition to being more reliable byremoving the unnecessary intermediate electric to air system thatincreases complexity and cost.

SCOPE OF THE INVENTION

The above presents a description of the best mode contemplated ofcarrying out the present invention, and of the manner and process ofmaking and using it, in such full, clear, concise, and exact terms as toenable any person skilled in the art to which it pertains to make anduse this invention. This invention is, however, susceptible tomodifications and alternate constructions from that discussed abovewhich are fully equivalent. Consequently, it is not the intention tolimit this invention to the particular embodiments disclosed. On thecontrary, the intention is to cover all modifications and alternateconstructions coming within the spirit and scope of the invention asgenerally expressed by the following claims, which particularly pointout and distinctly claim the subject matter of the invention:

1. A refuse vehicle including a lifting arm mounted on a side of thevehicle, said arm having a grabber mechanism that grips a refusecontainer on the ground, a refuse storage body including a packer thatpushes refuse towards a rear door to compact the refuse, said rear doorupon being opened, and the body tilted, allows compacted refuse to bedischarged, a hoist for tilting said body, a first positive displacementpump with an associated first valve system in fluid communication with afirst drive mechanism that operates the packer, the rear door, and thehoist, a second positive displacement pump with an associated secondvalve system in fluid communication with a second drive mechanism thatoperates the lifting arm, said first and second valve systems eachincluding at least one closed-centered valve with a spool mechanismhaving a pressure compensator to maintain a constant flow rate of fluidthrough the valve regardless of differential in pressure across thevalve for any given position of the spool mechanism.
 2. The refusevehicle of claim 1 where the spool mechanism is controlled directly byan electrical/electronic control system that governs the operation ofthe spool mechanisms for the valves of the first and second valvesystems.
 3. The refuse vehicle of claim 2 where theelectrical/electronic control system includes a programmablemicroprocessor.
 4. The refuse vehicle of claim 3 including electronicactuation devices that, in response to electrical signals, operate thedrive mechanisms, said microprocessor programmed to control the movementof the spool mechanisms to adjust the speed and direction at which thedrive mechanisms move.
 5. The refuse vehicle of claim 4 where theprogrammable microprocessor is programmed to have at least oneinterlocking safety feature without the use of external mechanisms andvalves.
 6. The refuse vehicle of claim 5 where the interlocking safetyfeature is responsive to a signal from a sensor.
 7. The refuse vehicleof claim 1 where the lifting arm moves in and out and up and down andthe arm is continuously monitored.
 8. The refuse vehicle of claim 1where the lifting arm returns a refuse container that it is gripping tosubstantially an exact position at which the arm initially gripped thecontainer.
 9. The refuse vehicle of claim 1 where the drive mechanismfor the packer is controlled so that the packer smoothly stops andsmoothly reverses direction.
 10. The refuse vehicle of claim 1 where thepressure compensated flow control through each closed-centered valve ismaintained at a constant flow of hydraulic fluid regardless ofpressures.
 11. The refuse vehicle of claim 1 where the lifting arm has apredetermined motion shape profile that is a function of shaping of anelectrical control signal.
 12. The refuse vehicle of claim 11 where themotion profile is shaped so that the up/down and in/out motions of thelifting arm to accelerate and decelerate to minimize the cycle time,allows time for refuse to drop out of the refuse container in a dumpposition, and provides timely and strategically placed decelerationswhen the container is returned to ground after dumping the refuse. 13.The refuse vehicle of claim 1 including a programmed regenerativefeature for the motions of the lifting arm and packer.